Conventionally, there has been known a vapor-liquid separator which centrifugally separates a blow-by gas leaking from a combustion chamber of an automotive engine into gas and oil, for example in JP-A 2005-146972 and JP-A 2003-49625.
JP-A 2005-146972 discloses a vapor-liquid separator which is provided with an oil storing tank (6) for improving oil dischargeability, and is provided in an oil discharging port (61) of the oil storing tank (6) with a check valve (7). This check valve closes the oil discharging port (61) during an operation of the engine and opens the oil discharging port (61) at a time of stopping the engine.
In addition, JP-A 2003-49625 discloses a vapor-liquid separator in which a oil discharging port (46) is disposed on a wall of the separator main body.
However, according to the vapor-liquid separator in JP-A 2005-146972, the structure is made such as to store the oil within the tank intermittently during the operation of the engine and a large capacity of tank is necessary. In addition, since the vapor-liquid separator has the check valve and the opening and closing mechanism thereof, and the structure is complicated. Further, there is a risk that a sticking of a valve body, a freezing or the like is generated due to an increase of an oil viscosity, an operation in a cold district or the like.
Moreover, according to the vapor-liquid separator in JP-A 2005-146972, when the hole diameter of the oil discharging hole is large, the oil separated from the oil discharging hole sometimes flows backward at the time of sucking the blow-by gas. On the other hand, when the hole diameter of the oil discharging hole is small, there is a problem that the oil dischargeability is lowered.